Hard color-singlet exchange in dijet events in proton-proton collisions at √s = 13TeV

Abstract

Events where the two leading jets are separated by a pseudorapidity interval devoid of particle activity, known as jet-gap-jet events, are studied in proton-proton collisions at root s=13 TeV .The signature is expected from hard color-singlet exchange. Each of the highest transverse momentum (pT) jets must have pj et T>40 GeV and pseudorapidity 1.4<|?jet|<4.7, with ?jet1?jet2<0 ,where jet1 and jet2 are the leading and subleading jets in pT, respectively. The analysis is based on data collected by the CMS and TOTEM experiments during a low luminosity, high-?? run at the CERN LHC in 2015, with an integrated luminosity of 0.66??pb?1. Events with a low number of charged particles with pT>0.2?? GeV in the interval |?|<1 between the jets are observed in excess of calculations that assume only color-exchange. The fraction of events produced via color-singlet exchange,f CSE , is measured as a function of p jet 2T, the pseudorapidity difference between the two leading jets, and the azimuthal angular separation between the two leading jets. The fraction f CSE has values of 0.4�1.0%. The results are compared with previous measurements and with predictions from perturbative quantum chromodynamics. In addition, the first study of jet-gap-jet events detected in association with an intact proton using a subsample of events with an integrated luminosity of 0.40??pb?1 is presented. The intact protons are detected with the Roman pot detectors of the TOTEM experiment. The f CSE in this sample is 2.91�0.70(stat)+1.08?1.01(syst)times larger than that for inclusive dijet production in dijets with similar kinematics.